The basic elements of the controllable switching device are an electrode system, comprising a working discharge gap, high-voltage insulators and a trigger assembly. The trigger assembly is the most critical element of the device and it basically affects the service time, reliability and timing characteristics of the switch. Triggering of the switch can be accomplished by various means, including triggering from hot cathode and by laser shot, however prevailing methods are the triggering with a discharge over a dielectric surface, a discharge on a semiconductor element and a triggering mechanism based on an auxiliary glow discharge.
When operated the switch is required to have extremely fast rise of current in an anode circuit with low and stable time delay when triggering pulse with minimum energy is applied to the a trigger assembly, as well as a sufficiently broad range of operating gas pressure in the switch, ensuring long-term operation of the switch under conditions of gas absorption in the discharge and change of electrodes temperature. The parameters significantly depend on triggering mechanism and configuration of trigger assembly—starting electrode.
For the switch to operate normally it is required that the trigger part provides stable and low (less than 1 μs) delay time and, secondly, the operational life is remarkably longer than the service life of the basic electrodes of the device.
One such switch—a controllable gas-discharge device (pseudospark switch), taught by application EUP N 0433480, cl. H01T 2/02, pub. 26.06.91 as well as US patent “Gas-electronic switch (pseudospark switch)” U.S. Pat. No. 5,091,819, Feb. 25, 1992, issued to J. Christiansen et al., discloses a thyratron, comprising an anode and a cathode with central holes, connecting cavities in the electrodes with main gap and trigger electrode. The trigger electrode with adjacent cathode serves as a unit triggering main discharge between electrodes of the switch. Triggering of the main gap is exercised by plasma injection from the trigger electrode under firing potential through the holes in the cathode.
The known design suffers from a limited range of working gas pressure, has complicated triggering circuit configuration and low dielectric strength, which is conditioned by a presence of charged particles close to the cathode hole, generated in an auxiliary discharge, as well as high temporal instabilities (pulse edge instability, time jitter), high pulse delay time. The design is not effective for switching of energy exceeding 500 J at operating frequencies less than 100-200 Hz.
Another special geometry of pseudospark switch trigger part was investigated by M. Iberler, R. Bischoff, K. Frank, I. Petzenhauser, A. Rainer, J. Urban, “Fundamental Investigation in Two Flashover-Based Trigger Methods for Low-Pressure Gas Discharge Switches”, IEEE Trans. Plasma Sci., vol. 32, no. 1, p. 208-213, 2004. The geometry has a dielectric (∈=2400) disc of 15 mm in diameter and thickness of 0.8 mm. The disc has a one-side metallization to provide reliable contact with metal substrate, whereas from another side it has pectinated contacts with a hollow electrode.
In the beginning of the switch operation a dielectric igniter gives high density of emitting charge, low delay time. However under real conditions due to the fact that in this device the effect of solid dielectric surface breakdown is usually used, with time electrodes materials are sputtered over the dielectric surface, which leads to reducing of emitting charge, whereas timing characteristics of the switch become very unstable and service life is limited by damage of the ignition unit.
In regimes with low operating frequency and high switching charge per shot it is the most advantageous to use semiconductor material in the igniter unit. Having relatively low specific resistance, this material is relatively more stable in terms of the aforesaid characteristics in case of conducting films evaporation in operating switch. Also in this device at the initial stage of discharge development a discharge current passes through the bulk of the igniter, that is why surface properties a lesser degree influence its characteristics within service life. The initiating of breakdown between electrodes contacting the semiconductor does not require high field strength, as it does in case of dielectric, which promotes longer operating capacity of the igniter even in case of substantial electrode erosion.
The close analogy to the presented invention is        1807798, H01 J17/44, Oct. 1, 1990.  No26 Sep. 20, 1997) {Controlled gas-discharge device, Bochkov V. D., Zaidman S. Sh. and Vosmerick Yu. M., Patent Russian Federation No. 1807798, H01 J17/44, Oct. 1, 1990, published in Bulletin of Inventions No26 Sep. 20, 1997}, comprising an anode and a hollow cathode with plate, facing the anode and having holes, as well as a hollow trigger electrode with a semiconductor igniter, placed in the cathode cavity. Further in the trigger assembly on the semiconductor igniter a contact element is placed, having a plurality of pins, mechanically connected with the igniter surface and galvanically coupled with the trigger electrode.
In the described switch with low buffer gas pressure an ignition device based on semiconductor material with a contact element, connected with a trigger electrode, is used. The contact element in gas-discharge device represents a loop made of a refractory metal wire, wrapped by a copper wire. The wraps of the wire comprise a ribbed surface, comprising a plurality of pins, providing a multidrop contact network.
The above construction have had one or more disadvantages, including the possibility to have only one contact element with a plurality of pins, which reduces life and demands strict compliance of trigger voltage polarity. Another drawback is an insufficient stability of timing parameters as well as relatively high pulse currents required for the switch triggering since even small contact area in case of linear V/A characteristic of the igniter gives too low transient resistance. The need to increase triggering power leads to a growth of power losses on the igniter, reduction of operating temperature range, degradation of frequency and service life of the switch.